Reproducing engineering data



June 14, 1960 Q sHUERT REPRODUCING ENGINEERING DATA Filed June 2a, 1958 INVENTOR. C5674 6. .S/IMFRT United States Patent ice 2,940,850 Patented June 14, 1960 REPRODUCING ENGINEERING DATA Cecil G. Shuert, Grosse Pointe, Mich. (1.3550 Conant, Detroit 12, Wayne County, Mich.)

Filed June 26, 1958, Ser. No. 746,065

Claims. (Cl. 96-27) This invention has to do with reproducing engineering data, and relates to the accurate and identical reproduction of loft layouts, and particularly to reproduced layouts to be used for drafting or additional drafting work. This application is a continuation-in-part of application Serial No. 346,461 filed Apr. 2, 1953.

It has been standard practice in the commercial production of airplanes, ships, automobiles and the like, to use painted metal sheets for the layout surface. On this painted layout surface is made a full scale master drawing of the particular new design desired, usually in pencil. A process for making a reproduction of such a master drawing on to a dimensionally stable metal surface is disclosed in the application to Stewart, Serial No. 5,575, filed Jan. 31, 1948, now forfeited, wherein is disclosed a reflex process of photo-mechanically transferring the lines of a master drawing on a loft or draft to a photo-sensitive surface presented by a sheet of painted size retaining material such as aluminum or steel, this being accomplished by a contact method utilizing one or more negatives with transparent lines; the master drawing being reproduced on the painted steel in the form of sharp clean inked lines of the exact same dimensions as the lines of the master drawing. Such metal reproduction of the replica type as made by the Stewart process, usually consisted of an ink coated bichromate line on a white background, and had the disadvantage of a line which was raised minutely and which was coated with ink; such raised line, if protected by a lacquer coating, would be suitable for reference work, but a loft draftsman could not Work over the lacquer. However, the unprotected raised line would not be suitable for additional drafting because such line would be subject to smearing and abrad-- ing. The making of loft drawings often takes several months, and the surface of the drawing must withstand the abrasion of the draftsmans body and often many major erasures or changes are made.

The process of the present invention is an improvement over the process disclosed in said Stewart application Serial No. 5,575, in that the labor costs of printing the metal reproductions are reduced approximately 75% the product of the present invention is an improvement over the product of the said Stewart application in that the reproduced lines forming the accurate replica of the original drawing are flush with the surface of the metal reproduction and hence do not readily wear away under drafting use; furthermore, the surface of the loft reproduction is free of any gelatin or emulsion, leaving exposed the normal surface which readily adapts itself to the drafting pencil.

Essentially the present invention makes use of a negative or negatives of the type disclosed in said Stewart application wherein the negative is formed of glass with transparent lines and an opaque coating between the lines;

the negative preferably being formed in accordance with the Stewart process wherein. a sheet of transparent-size retaining material such as plate glass is coated on one surface with a very thin emulsion of the ammonium di chromate type which is temporarily photo-sensitive, the emulsion side of the glass being placed in face contact with the loft drawing to be reproduced, the emulsion being exposed to light transmitted through the glass and being reflected from the drawing whereby the emulsion contacting the lines of the drawing is rendered water soluble and the remaining emulsion water insoluble, the exposed emulsion next being rolled up with etching ink and the water soluble portion of the emulsion and the etching ink covering the same being removed, such as by water spray, to form clear sharp transparent lines on the negative identical with the lines of the original drawing.

I have found that it is not only possible to obtain replica lines on metal reproductions that are flush with the surface, but this can be done much cheaper than by the Stewart ink line method, by utilizing a dye mixed with an emulsion sensitizer. After having obtained the negative with transparent lines, the mixing of the dye with the sensitizer makes it extremely easy to photomechanically transfer the lines from the master loft to the metal reproduction, the essential steps consisting of painting a sheet of metal such as aluminum with a white paint, preferably a slightly porous primer of the synthetic lacquer type, the porosity of the paint is important in that it will allow the sensitizer to be sucked into the pores of the paint and be bonded into the painted surface, and also offers a correct tooth to a 91-1 drafting pencil. The emulsion used is preferably one of the bichromate type and the dye used is preferably a casein vehicle dye, the mixture of emulsion and dye being relatively thin.

This combination dye and sensitizer is sprayed over the surface of the painted base as a very thin uniform coating; the negative is then applied to the sensitized surface, exposed to light to harden the sensitizer, where exposed through'the transparent lines, and the exposed base or panel is then developed with water to remove the unexposed sensitizer. The resulting line, which only remains colored in accordance with the selected dye, is flush with the surface of the paint, the dye and sensitizer having penetrated into the pores of the paint become a part of the paint. The surface of the painted panel is then cleaned with an oxalic acid solution and rinsed with clear water to, whereby when dry, present a replica of the master drawing by means of very tough durable and accurate lines which will not smear or abrade and which form a part of a perfectly flat uncoated loft drafting surface.

The labor saving in using my process for printing the reproduction stems principally from the elimination of the step of ink coating of the exposed sensitizer as disclosed in the Stewart application and the probability of damage to the print during development and the use of relatively inexperienced labor to make prints by my process. Originally about two hours were required to make a five by fourteen feet print by the Stewart process, whereas with my process such prints can be produced in thirty minutes.

A further feature of the present invention which ties in with the production of an image line, and permits drawing Without interference, has to do with the manufacture of gridded layout panels. Since loft drawings have become a must in connection with aircraft, airframes and automotive bodies, due to the high degree of accuracy required, it has been customary for the draftsman to lay out accurate squares, usually five or ten inches on the loft surface, which squares become the base for accuracy control throughout the engineering and tooling phases. The time required by a highly skilled draftsman for the erection of the proper geometric pattern to assure accurate grid pattern layout on a sheet of painte'd' metal five feet by fourteen feet is approximately twenty none'of these'methods have produced accurate grid patterns economically: Since it is now possible, as above described, to'print lines or; painted metalsurfaces, which lines are'fiush'with' the surface,- I'have conceived the idea ofco' mbining the registration feature as set forth in Stewart application-Serial No; 5,575 with'an accurate negative of the required grid pattern to print'any size grid pattern on met'ali The manner of achieving'this a'ccurateneg'ative is-b coating a 'pl'ate 'glass support- (about forty-eight by seventy four inches in size) with a bichromate sensitizer, and then completelyexposing the sensitizer coating to a light source to effect an overall hardening of the bicr'oniate' sensitizer, which hardening action firmly bonds" the sensitizer to the glass support.

7 any attemptsl'iav'e' been madetoin'iprove the metliod' of laying in'gr'id patterns, such'as 'by gang scribers, but

The hardened bichromate coating is then coated over all 7 with etching ink.

This coated glass support is then placed in position on a Swissboring machineand the fine lines are scribed through the coating to the glass support, resulting in transparent sharply defined lines. A machine such as the Swiss boring machine permits the accurate placement of both the horizontal and vertical lines to create the de-- sired grid pattern and also the placement of the regist'ration marks in the proper locations to make possible the'printing" of large grid panel patterns commonly five feet by fourteen feet. Having obtained the master grid negative it isonly a matter of thiry minutes to, in accordance with the process set forth in the second above paragraph, print-the large" grid panel layout'and to duplicate the same as mauy times as desired from the mastennegative. All such panels are identically accurate and'sirnilar one to another. 7 7

Other features have to do with detailed steps of the method, structural details and formulae, all of which will bemore; fullyand specifically set forth in the following specification and claims. 7

Inherit-swings; i I Figure 1 is air-enlarged sectional perspective view of a replicapanel' illustrating how the lines on the surface are bonded into but flush with'thetop of the print Figure'Z isan enlarged sectional view of a scribed griddedlayo'ut'p'anel. i V i g Figure 3 is anenlarged sectional perspective view of a master negative used for making gridded layout panel's. Figure 4 is a perspective view of a scriber used for scribing out reproduced gridpatterns.

While the present process particularly relates to the photo mechanical reproduction of full sizedloft drawings, the lines of which are flush with the surface of the loft, it is also concerned with the accuracy of the original master loft drawing, because this accuracy is reproduced right down through the entire process. It is therefore thought that the present invention may be best understood .byfirst describing the method of making the gridded panel layout on which is placed the original loft drawing. 7

Preparation of master negative-Select a good grade of plate glass, approximately 48".); 74" x 1 thick having surfaces as fiat and smooth as commercially possible, preferably made from a glass formula permitting maximum light transmission and minimum discoloration characteristics. Coat this glass, in a machine called a whirler, with a light sensitive solution, as described in said Stewart application Serial No. 5,575 for the preparation of a negative. 7

An effective light senstive solution may be prepared a follows: 7

. 4 20oz. fresh egg albumen V 200 grains ammonia dichromate .40 drops ammonium hydroxide 1 gallon distilled water a Beat egg albumen (whites) well with power beateruse some of distilled water to dissolve dichromatemix water, albumen and dichromate solution thoroughly, add

ammonium hydroxide. Filter carefully through cotton at least twice, let stand three days before using and filter again just prior to use. Keep clean and free of dirt.

Albusol solution can be substitute d -use approximately same quantity of albumen but adjust according to negative problem. Albusol'sensitizer solution can be used immediately after filteringthrougn filter paper. Keep stored in dark bottles 'ina cool place." Solution should be good for thirty days. I a

After having obtained a uniform thin dry emulsion on the plate, such sensitive surface is exposed overitscomplete area, using a suitable light source to render the total sensitive surface insoluble in water. The complete surface of exposed emulsion is next coated with a relatively thin coating of black ink and lamp black, as described in said Stewart application. The black ink coating may be an etching ink having a proportion of vli'rederiksens etching. ink and 50% Perfection etching ink. The lamp black may be applied to the ink coating by using a sifter and a cotton swab, thejexcesslanip black being blown off with air, the oil surface of the ink holding the required lamp black in place. Such' a base member with a glass plate 10, photo-senstive emulsion 11, and surface of etching ink andlamp black 12 is shown in Figure 3. e V v The thuscoated glass plate is placed, coated. side up, in the bed'of a Swiss boring'machine (or equivalent machine tool) and locked in place. Using a spring mounted scribing tool clamped in the head. of the machine, the'desired grid pattern is cut in the coated surface of the glass to expose the glass surface in the lines clearly and completely. These accurate lines are usually cut entirely across the plate, usually either five or ten inches apart, the plate or the head'then rotated 90? and similar lines cut' to form accurate five or ten jinch squares.

The scribing :tool controls the width'of the lineppreferably about .003" to .004", and the springmou'nting of the scribe tool permits it to follow the surface of the plate 1 glass without scratching the glass and only removing the coating. Such ascribed line is shown at 13 in Figure 3.

The'same scribing tool is used to cut a registration device, suchas shown at" 14 in Figure 3, in each of the four corners'of the master negative. A completed cutting of the pattern in the coated surfaceof the glass presents a concise negative embodying lines of a controlled wvidth and definition. The negativethus produced is then retouched, if required, to render opaque any blemishes in the background area caused by handling, and is then coated with a clear lacquer such as Dinoc #2155 manufactured by the Dinoc Company.

While the master negative just described may be used for making positive print gridded layout panels, it is, because of its original cost, preferably used only for the purpose of making a positive print on plate glass A thick, and in turn this PQSitive print is carefully preserved and used only to' make the actual printing negatives on A" plate glass. These supplementary .glass' positives and negatives are made by coating glass with a suitable sensitizer which. is then exposed and developed as described in said Stewart application SeriaYNo. 5,575.

Figure 1, usually about five feet by fourteen feet and" preferably aluminum, is painted to'pro'duc'e a surface 16' 5 about .007 inch to .010 inch depth when finished. The paint used for this surface is preferably a slightly porous primer type synthetic lacquer known as a combination primer surfacer such as Du Pont 65-1050 Preparacote (a high alkyd resin type primer surfacer), or comparable paints made by Ditzler, Acme, or Sherwin-Williams, the important point being that the paint when dry, should have sutficient porosity as to suck in or accept the sensitive bichromate coating so that the bichromate coating, when hardened by exposure, will be bonded to the painted surface. When dry, the porosity of the paint surface is enhanced by sanding or rubbing so as to offer the correct tooth to a 9H drafting pencil.

The dry painted surface 16 is next sensitized by ap-' plying the following formula with a spray gun-- Example I 1% oz. ammonium bichromate 50 oz. Albusol Water (alcohol can be substituted for a portion) to make a gallon 1% oz. casein vehicle dye (any selected color) (Lamp black or commercial opaque) 4 oz. glue Dye is dissolved in water or alcohol and then mixed with other materials.

Albusol is an aqueous solution of albumin marketed by Mallinkrodt Chemical Company of St. Louis, Missouri.

From the skill and experience in the making of layout panels under the present process I have found it best to apply a sensitized coating made up of several finely atomized applications. The combined dye and sensitized solution, being applied in a plurality of finely atomized applications, goes into the pores of the paint whereby the. surface of the paint still defines the top surface of the panel. I

The sensitized panel is next placed in a vacuum frame and the master negative, previously described, is placed to cover the left end of the panel with the coated surface 12 of the negative in contact with the sensitized surface of the panel. The frame is locked, vacuum applied, and exposure is made using a high intensity light source, all of which steps are disclosed in said Stewart application Serial No. 5,575. The negative is then removed and the right hand registration device area, as printed on the. panel by light shining through the device 14 such as shown in Figure 3, is then locally developed'by using a water wet cotton swab. The negative is then moved to the right to register the left hand registration devices 14 of the negative to the registration marks just developed on the panel. The exposure procedure as just described is repeated. This registration and exposing is repeated until the entire panel is completely exposed.

The panel is then placed in a large sink and developed with flowing water and swabbed off with a cotton or sponge. The high intensity light, which has shone through the scribed openings 13 in the negative, will have rendered the sensitizer and dye (which is held bonded in the pores of the paint) insoluble, such as shown at 17 in Figure 1. Developing of the panel in the sink with the cotton or sponge swab removes the excess unexposed. and soluble sensitizer and dye with the result that lines 18 corresponding to the transparent lines13 on the negative remain, colored according to the selected dye. Any bichromate stains can be removed with a weak oxalic solution or similar bleach and the panel rinsed ofi.

When dry, the result is a panel with fine grid lines of the selected sensitizer color and an accuracy of plusor minus .003" or less over the total panelwith no accumulated error. Heretofore such accuracy has never been achieved. Furthermore the sensitizer dye forming the lines is held in the pores of the paint presenting a drafting surface defined by the paintitself with no ridges. In other words, the lines forming the grid panel are flush with the surface of the painted coating because the line pigmentation is essentially bonded into the pores of the paint and as a result the lines do not readily-wear away under drafting use. Every gridded layout panel produced in this manneris identical with every other panel produced by the same method.

Many drafting rooms require that the grid pattern on the panel be scribed in the paint surface of the panel. I have found it possible to supply such a scribed gridded layout panel, having the same accuracy as the above described printed grid panel, by scribing out the lines 18 or" the printed gridded layout panel as follows: f

A scribed or cutting tool block as shown in Figure 4 is made of a block of transparent plastic 19 having wear plates 20 on each side thereof. Positioned to extend vertically to the center of this block is a carboloy tipped shaft 21 locked in place on a feed screw 22. A magnifier 23 is located in the block and positioned to be focused on the tip 24 of the cutting tool. The cutting point 24 is shaped to produce a cut as shown at 25 in Figure 2 and the depth of the cut is controlled by setting the cutter against a micrometer. By these controls the depth and Width of the out can be predetermined; as shown in Figure 2 the width of the cut is approximately .005" and the depth approximately .005 inch. 1 To produce a scribed line pattern on the above de-' scribed grid panel, a straight edge is placed onthe panel approximately parallel to the first line, such as 18 in Figure l, and distant from that line a space approximately the equivalent to the distance from the scribe point 24 to the outside of the scribe. block 19. Then; using the magnifier 23 the scribe block is positioned so that the cutter point 24 splits a line 18 on the panel when'the block 19 is snug against the straight edge. This line up operation is repeated for the opposite end of the line and the scribe block is then pulled along the straight edge and the scribed point pulled through the line, completely removing the line 18 from the panel, and replacing it with a scribed line 26 as'best shown in Figure 2; Figure 2 also showing the sensitizer dye line 17 in dotted lines.

As will be seen from Figure 2, the scribedline 26 is a true V in shape, the low point of the line being the true center of the line. Using this procedure, all the lines 18 on the panel are replaced by scribed lines. Automatic proof of the accuracy ,of the pattern is at all times visible because each line must be completely cut out by the scribe to maintain accuracy. Having completed the scribing operation, the scribed lines may be blacked or colored using suitable pigments or' dyes and the panel cleaned up by lightly wet sanding to the desired finish. The white panel with colored lines is now ready for draftmg purposes requiring a scribed pattern and maintains an accuracy of plus or'minus .003 inch.

' Photo-mechanically reproducing engineering draft or loft drawings.-After a loft drawing has been made on a gridded layout panel of the type previously described, either colored line or scribed line, it is often desirable to have many reproductions of this loft drawing made on painted metal to produce exact loft reproductions. Previously reproductions of master loft drawings onto dimensionally stable metal surfaces in the form of ink lines have been accomplished by the process disclosed in Stewart application Serial No. 5,575, and in the present invention use is made of some of the steps disclosed in said Stewart application except that instead of reproducing as an ink line the drawing is reproduced as a colored flat line and in so doing the labor cost of printing such reproduction is reduced to approximately Specifically, the master negative of the master loft drawing is prepared in exactly the same manner as described in said Stewart application. In fact, the master. negative of the loft drawing is prepared in the same manner as previously described in this application under the heading Preparation of'master'negatiw for gridded Solution .A

layout-panels, except that after the bichromate sensitizer solution has been applied to theglass plate, the master loft drawing is placed in face contact with said light sensitivefcoating and the intense light shinin through the negative will render the sensitive surface on the glass plate msoluble in water except for those surfaces lying underneath the lines of the drawing. The exposed emulsion on the glass surface is then coated with a rela-' tively thin coatin'g of black ink and lamp black as previously described in connection with the .makingof the gridded layout panel negative and as described in said Stewart appli [tion Next instead of scribing lines on the exposed surface as is done in making the gridded layout panel, the exposed negative of the master loft drawing is subjected to a fine spray of air and-water to re move the soluble emulsion and backing ink inthe form of distinct clean lines. 7 'i te': the negative with transparent lines is formed to:

print the: loft drawing of the negativeon to a metal sure face, such reproduction metal surface is painted as he; scribed'in connection 'th the making of gridded layout panels in that it is painted with a slightly porous primer of the synthetic lacquer type to achieve bonding of the final lines and -to present a surface adaptable to a drafting pencil. The dry painted surface of the reproduction panel is then sensitized with a solution of combined dye and sensitizer In the winter-time or with controlled humidity it is possible to use a dyetand sensitizer solution'of thetype previouslyset forth in Example I in the same manner as previously described, namely, with several finely atomized applications, such applications being fine so that the dye sensitizer solution goes into the pores of the paint. 7 d

If low or controlled humidity conditionsare not 'pres- 'ent,-then it is desirable'to use a dye sensitizer solution as follows: 7 7

' Exampl e ll 2% ounces ammonium bichromate 40 ounces Albu'sol 4 ounces glue Water to make 1 gallon Solution B:

Carters Poster. Black, 'Mural-Tonc or equivalent casein vehicle dye in any color 7 To use: Combine 4 parts Solution A with 1 part Solution B. a Application: Spray one fine almost dry undercoat of Solution A and then spray about five fine almost dry over coats of combined Solutions A and B.

Afterthe dye sensitizer coating on the reproduction panel is dry, it is placed in a vacuum frame and the developed coated surface of the negative,'wbich is similar to the negative shown in Figure 3, is then placed in contact with the dye sensitizersurface of the panel and the vacuum locked assembly exposed to a high intensity light source as previously described in connection with printing of the layout panel. I The exposed reproduction panel is then removed to a sink, developed with water using acotton or sponge swab to remove the soluble dye sensitizer and leaving only a colored line as at- 27 in1Figure l, which line is identical tintall respects with the line 18 used in forming a gridded layout panel. The dye sensitizer being rendered insoluble. by the light and being bonded in the pores of the paint, presents a colored line of better quality and usefulness than the ink line of the Stewart print by eliminating the undesirable characteris tics of the ink line in that it will not smudge and will not abrade because it is flush with the paint'surface; Fur thermore, if it is desired at some future time to change t I l tion line porouspaint surfaceis an. idcalsurface for draft mg purposes and, furthermore, such drafting surface. is identical to thatof the original layout panels in that erasmg of lines andnew drafting is easily carried out.

In the case of large loft reproductions, a multiple number of negatives using registered marks, as previously described, could be used in-reproducing the large master loftdrawing; it will be'understood that all the steps previously described in the making of gridded layout panels, master loft drawing negatives and reproduction panels may be carried out in normal light. It will also be understood that reproduction material is not confined to aluminum but can beany material preferably one having dimensionally stable properties. V

Regardless of whether the loft drawing is printed on the painted metal or'whether the master grid lines are printed on the painted metal, or. whether the printed lines are cut out to form a sc 'bed layouttpanel, it will be seen, because the dyelsensitizer mix enters into and is bonded into the pores of the, paint, that "the entire exposed surface of the printed and/or scribed panel is free of any emulsion, making such surface ideal for the use of a drafting pencil in drawing over the reproduced lines or when erasing such reproduced lines: for changes.

I have also discovered that it is possible to use a metal print emulsion by combining silver .nitrate'with ammonium bichromate instead of dye and ammonium bichromate to obtain clear distinct lines instead of fuzzy lines. However, such a silvernitrate print emulsion is so much more expensive than a dye bichromate emulsion as to make it prohibitive. It will be understood, however, that while the ammonium bichromate sensitizer is preferred and best from a commercial andfeconomic standpoint, that other light" insolubilized sensitizers, known to those skilled in the art, for example, the potassium bichromate type, may be used. 7

From the foregoing it will be apparent and obvious the the gist of the present invention lies .in the use of a the drawing, may be of any convement thickness and instead of being coated' with a porous synthetic lacquer as previously'described, such metal surface may itself be rendered porous to provide a porous surface capable of substantially completely absorbing the dye sensitizer solution. In the case of a metal surface, such as an. aluminum sheet, the requisitevporosity may be imparted to it by etching or abrading, such as by sand blasting, cal: endering, or sanding with a #220 grit. In such an arrangement wherein the metal sheet is' in itself formed with a porous surface for substantially completely absorbing the dye sensitizer solution, the crossjhatched area designated 16 in Figure 1, instead of representingpaint, represents the porous surface of the metal.

Itwill also be observed that the reproduction panel 16 may bed a material other than metal. For example, a dimensionally stable plastic sheet. Inthe case of a dimensionally stable plastic sheet, a porous surface on one side thereof canbe imp'artedthereto as .discussed l. The steps in the process of photomechanically' trans-' ferring'cf drawings from'one dimensionally stable surface to a reproduction dimensionally stable surface by the contact method utilizing a negative with transparent lines andopaque coating between the lines, which comprises coating said reproduction surface with a white synthetic lacquer primer paint which when dry contains pores, drying the paint, abrading the surface of the dry paint, such abraded surface presenting a tooth for penciling and being readily absorptive of a thin sensitizer solution, impregnating said paint with a combined dye and dilute organic colloid ammonium bichromate sensitizer 10 solution, said combined dye and sensitizer solution being capable of being substantially completely absorbed by said paint and the amount of said solution being regulated to provide substantially complete impregnation by absorption so that said sensitizing solution is substantially com pletely absorbed by said paint, locating said negative in face contact with said dye sensitizer surface, transmitting light through said transparent lines torender insoluble the dye sensitizer in the pores of the paint underlying said transparent lines, Washing out the soluble dye sensitizer solution from the surface and pores of the paint to leave a positive reproduction of said transparent lines of the negative in the shape of colored lines formed by the insoluble dye sensitizer solution in the pores of the paint and presenting colored lines substantially flush with the surface of the paint.

2. A process as set forth in claim 1 wherein said organic colloid ammonium bichromate sensitizer solution includes albumen as the primary constituent of said organic colloid.

3. A process as set forth in claim 1 wherein said porous synthetic lacquer primer paint has a high alkyd resin content.

4. A process as set forth in claim 2 wherein said porous, synthetic lacquer primer paint has a high alkyd resin content.

5. The steps in the process of photo-mechanically transfen-ing of drawings from one dimensionally stable surface to a reproduction dimensionally stable surface by the contact method utilizing a negative with transparent lines and opaque coating between the lines, which comprises using a dimensionally stable reproduction backing material having a porous surface which presents a tooth for penciling and which is readily absorptive of a thin sensitizer solution, impregnating said porous surface with a combined dye and dilute organic colloid light insolubilized bichromate sensitizer solution, said combined dye and sensitizer solution being capable of being substantially completely absorbed by said porous surface and the amount of said solution'being regulated to provide substantially complete impregnation by absorption so that said sensitizing solution is substantially completely absorbed in the pores of said surface, locating said negative in face contact with said dye sensitizer surface, transmitting light through said transparent lines to render in- 5 soluble the dye sensitizer in the pores of said surface underlying said transparent lines, washing out the soluble dye sensitizer solution from on and within said porous surface to leave a positive reproduction on said transparent lines of the negative in the shape of colored lines formed by the insoluble dye sensitizer solution in the pores of said surface and presenting colored lines substantially flush with said surface.

6. A process as set forth in claim 5 wherein said sensitizer solution is ammonium bichromate.

7. The steps in the process of photo-mechanically transferring of drawings from one dimensionally stable surface to a reproduction dimensionally stable porous surface by the contact method utilizing a negative with transparent lines and opaque coating between the lines, which comprises abrading said reproduction surface, said surface being readily absorptive of a thin sensitizer solution and presenting a tooth for penciling, impregnating said porous surface with a combined dye and dilute organic colloid light ins'oliibilize'dbichromate sensitizer s6: lution, said combined dye and sensitizer solution being capable of being substantially completely absorbed by said porous surface and the amount of said solution being regulated to provide substantially complete impregnation by absorption so that said sensitizing solution is substantially completely absorbed in the pores of said surface, locating said negative in face contact with said dye sensitizer surface, transmitting light through said transparent lines to render insoluble the dye sensitizer in the pores of said surface underlying said transparent lines, washing out the soluble dye sensitizer solution from on and within said porous surface to leave a positive reproduction on said transparent lines of the negative in the shape of colored lines formed by the insoluble dye sensitizer solution in the pores of said surface and presenting colored lines substantially flush with said surface.

8. The steps in the process of photo-mechanically transfern'ng of drawings from one dimensionally stable surface to a reproduction dimensionally stable surface by the contact method utilizing a negative with transparent lines and opaque coating between the lines, which comprises coating said reproduction surface with a white porous synthetic lacquer primer paint which when dry contains pores, drying the paint, abrading the surface of the dry paint, such abraded surface presenting a tooth for penciling and being readily absorptive of a thin sensitizer solution, impregnating said paint first with a thin undercoating of a dilute organic colloid light bichromate sensitizer solution and then with an overcoating of said sensitizer solution combined with a dye, said solutions being ca.- pable of being substantially completely absorbed by said paint and the amount of said solutions being regulated to provide substantially complete impregnation by absorption so that said sensitizing solutions are substantially completely absorbed by said paint, locating said negative in face contact with said dye sensitizer surface, transmitting light through said transparent lines to render insoluble the dye sensitizer in the pores of the paint underlying said transparent lines, washing out the soluble dye sensitizer solution from the surface and pores of the paint to leave a positive reproduction of said transparent lines of the negative in the shape of colored lines formed by the insoluble dye sensitizer solution in the pores of the paint and presenting colored lines substantially flush with the surface of the paint.

9. A process as set forth in claim 8 wherein the sensitizer solution is ammonium bichromate.

10. The steps in the process of photo-mechanically transferring of drawings from one dimensionally stable surface to a reproduction dimensionally stable surface by the contact method utilizing a negative with transparent lines and opaque coating between the lines, which comprises using a dimensionally stable reproduction material having a porous surface which presents a tooth for penciling and which is readily absorptive of a thin sensitizer solution, impregnating said porous surface first with a thin undercoating of a dilute organic colloid light insolubilized bichromate sensitizer solution and then with an overcoating of said sensitizer solution combined with a dye, said solutions being capable of being substantially completely absorbed by said porous surface and the amount of said solutions being regulated to provide substantially complete impregnation by absorption so that said sensitizing solutions are substantially completely absorbed in the pores of said surface, locating said negative in face contact with said dye sensitizer surface, transmitting light through said transparent lines to render insoluble the dye sensitizer in the pores of said surface underlying said transparent lines, washing out the soluble dye sensitizer solutioqr f ro gnron said porous surfgce f0 leave a positiveregrpduet'ion' 6f sgidirahsbaiem lines of the negative in the shape of co rejjd formed by the insoluble ,dye sensitizer solution in, the pdreg of said s11:- face and presenting coldrd' substantially'fllish with 5 said surface.

References Cited in tl i'e file qf fla is patent V UNITED STATES PATENTS Cr bus'e 3,1945 Terry Se t. 18, 1 94s S'taehIe, Dee, 12, 1950 Eis'horn Aug. 6, 1957 Scewrt Sept. '16; 1958 

1. THE STEPS IN THE PROCESS OF PHOTO-MECHANICALLY TRANSFERRING OF DRAWINGS FROM ONE DIMENSIONALLY STABLE SURFACE TO A REPRODUCTION DIMENSIONALLY STABLE SURFACE BY THE CONTACT METHOD UTILIZING A NEGATIVE WITH TRANSPARENT LINES AND OPAQUE COATING BETWEEN THE LINES, WHICH COMPRISES COATING SAID REPRODUCTION SURFACE WITH A WHITE SYNTHETIC LACQUER PRIMER PAINT WHICH WHEN DRY CONTAINS PORES, DRYING THE PAINT, ABRADING THE SURFACE OF THE DRY PAINT, SUCH ABRADED SURFACE PRESENTING A TOOTH FOR PENCILING AND BEING READILY ABSORPTIVE OF A THIN SENSITIZER SOLUTION, IMPREGNATING SAID PAINT WITH A COMBINED DYE AND DILUTE ORGANIC COLLOID AMMONIUM BICHROMATE SENSITIZER SOLUTION, SAID COMBINED DYE AND SENSITIZER SOLUTION BEING CAPABLE OF BEING SUBSTANTIALLY COMPLETELY ABSORBED BY SAID PAINT AND THE AMOUNT OF SAID SOLUTION BEING REGULATED TO PROVIDE SUBSTANTIALLY COMPLETE IMPREGNATION BY ABSORPTION SO THAT SAID SENSITIZING SOLUTION IS SUBSTANTIALLY COMPLETELY ABSORBED BY SAID PAINT, LOCATING SAID NEGATIVE IN FACE CONTACT WITH SAID DYE SENSITIZER SURFACE, TRANSMITTING LIGHT THROUGH SAID TRANSPARENT LINES TO RENDER INSOLUBLE THE DYE SENSITIZER IN THE PORES OF THE PAINT UNDERLYING SAID TRANSPARENT LINES, WASHING OUT THE SOLUBLE DYE SENSITIZER SOLUTION FROM THE SURFACE AND PORES OF THE PAINT TO LEAVE A POSITIVE REPRODUCTION OF SAID TRANSPARENT LINES OF THE NEGATIVE IN THE SHAPE OF COLORED LINES FORMED BY THE INSOLUBLE DYE SENSITIZER SOLUTION IN THE PORES OF THE PAINT AND PRESENTING COLORED LINES SUBSTANTIALLY FLUSH WITH THE SURFACE OF THE PAINT. 